Dynamic fixation assemblies with pre-tensioned cord segments

ABSTRACT

A dynamic fixation medical implant having at least two bone anchors includes a longitudinal connecting member assembly having a core portion made from at least one pre-tensioned flexible member and a cooperating pre-compressed surrounding outer sleeve. The sleeve surrounds the core and is disposed between cooperating rigid end members that are attached to the bone anchors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/927,111 filed May 1, 2007, incorporated by reference herein. This application also is a continuation-in-part of U.S. patent application Ser. No. 12/006,460 filed Jan. 3, 2008 that claims the benefit of U.S. Provisional Application No. 60/922,465 filed Apr. 9, 2007; U.S. Provisional Application No. 60/898,870, filed Feb. 1, 2007; and U.S. Provisional Application No. 60/880,969, filed Jan. 18, 2007; all of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to dynamic fixation assemblies for use in bone surgery, particularly spinal surgery, and in particular to longitudinal connecting members for such assemblies, the connecting members being attached to at least two bone fasteners.

Historically, it has been common to fuse adjacent vertebrae that are placed in fixed relation by the installation therealong of bone screws or other bone anchors and cooperating longitudinal connecting members or other elongate members. Fusion results in the permanent immobilization of one or more of the intervertebral joints. Because the anchoring of bone screws, hooks and other types of anchors directly to a vertebra can result in significant forces being placed on the vertebra, and such forces may ultimately result in the loosening of the bone screw or other anchor from the vertebra, fusion allows for the growth and development of a bone counterpart to the longitudinal connecting member that can maintain the spine in the desired position even if the implants ultimately fail or are removed. Because fusion has been a desired component of spinal stabilization procedures, longitudinal connecting members have been designed that are of a material, size and shape to largely resist flexure, extension, torsion, distraction and compression, and thus substantially immobilize the portion of the spine that is to be fused. Thus, longitudinal connecting members are typically uniform along an entire length thereof, and usually made from a single or integral piece of material having a uniform diameter or width of a size to provide substantially rigid support in all planes.

An alternative to fusion, which immobilizes at least a portion of the spine, and the use of more rigid longitudinal connecting members or other rigid structure has been a “soft” or “dynamic” stabilization approach in which a flexible loop-, S—, C- or U-shaped member or a coil-like and/or a spring-like member is utilized as an elastic longitudinal connecting member fixed between a pair of pedicle screws in an attempt to create, as much as possible, a normal loading pattern between the vertebrae in flexion, extension, distraction, compression, side bending and torsion. Another type of soft or dynamic system known in the art includes bone anchors connected by flexible cords or strands, typically made from a plastic material. Such a cord or strand may be threaded through cannulated spacers that are disposed between adjacent bone anchors when such a cord or strand is implanted, tensioned and attached to the bone anchors. The spacers typically span the distance between bone anchors, providing limits on the bending movement of the cord or strand and thus strengthening and supporting the overall system. Such cord or strand-type systems require specialized bone anchors and tooling for tensioning and holding the cord or strand in the bone anchors. Although flexible, the cords or strands utilized in such systems do not allow for elastic distraction of the system once implanted because the cord or strand must be stretched or pulled to maximum tension in order to provide a stable, supportive system.

The complex dynamic conditions associated with spinal movement create challenges for the design of elongate elastic longitudinal connecting members that exhibit an adequate fatigue strength to provide stabilization and protected motion of the spine, without fusion, and that allow for some natural movement of the portion of the spine being reinforced and supported by the elongate elastic or flexible connecting member. A further challenge are situations in which a portion or length of the spine requires a more rigid stabilization, possibly including fusion, while another portion or length may be better supported by a more dynamic system that allows for protective movement.

SUMMARY OF THE INVENTION

Longitudinal connecting member assemblies according to the invention for use between at least two bone anchors provide dynamic, protected motion of the spine and may be extended to provide additional dynamic sections or more rigid support along an adjacent length of the spine, with fusion, if desired. A longitudinal connecting member assembly according to the invention has an inner segment or core made from a cord or cords, the core being fixed at either end to substantially rigid segments, illustrated as rods or tubes, each rod or tubular structure attachable to at least one bone anchor. The core is surrounded by a spacer that is elastomeric. The longitudinal connecting member assembly is dynamically loaded prior to being operatively attached to at least a pair of bone anchors along a patient's spine. The tensioned inner core and the compressed spacer cooperate dynamically, both features having some flexibility in bending, with the outer spacer protecting and limiting flexing movement of the inner core. The spacer may include one or more grooves to aid in compression upon installation between the rigid elongate segments.

In particular, an illustrated inner core of a dynamic longitudinal connecting member according to the invention includes at least one and up to a plurality of tensioned ties, cords or strands surrounded by a compressible outer spacer. At least one end thereof, the cord or cords of the inner core are attached to a plate that is in turn integral with a rigid elongate segment, such as a solid rod or tubular segment. In one embodiment, the inner core includes a plurality of closed loops that are threaded through apertures in a pair of opposed plates, each plate being attached to a longitudinal connecting member, such as a rod segment. The inner core is then pre-tensioned by pulling the plates away from one another and a slitted outer spacer is received over the taunt cords while being compressed and then released between the plates. The plates compress the spacer while placing a distractive force on the cords of the inner core.

In another embodiment, cords are looped through apertures of one plate to attach the inner core to a first elongate member. The cords are also received through a bore of a non-slitted compressible spacer and further through a bore of a second elongate member. The cords are then pulled in a direction away from the plate to place the cords in tension and fixed in place by one or more processes, including placing and depressing a crimping ring at the end of the second elongate member, by directly crimping the second member, and/or by melting the cord or cords, for example. As tension is placed on the cords, the spacer is compressed by rigid plates located on either side thereof.

A variety of embodiments according to the invention are possible. Rods or other substantially rigid structures having different measures of rigidity may be connected according to embodiments of the invention. Either rigid lengths or flexible cords may be of greater or lesser lengths for attaching to one or a plurality of bone anchors.

OBJECTS AND ADVANTAGES OF THE INVENTION

An object of the invention is to provide dynamic medical implant stabilization assemblies having longitudinal connecting members that include both rigid and more flexible sections or lengths, the flexible sections allowing for at least one of bending, torsion, compression and distraction of the assembly. Another object of the invention is to provide such an assembly wherein a portion is pre-tensioned while a cooperating portion is pre-compressed. Another object of the invention is to provide such an assembly wherein the flexible section or sections are insertable into a protective outer sleeve. A further object of the invention is to provide such an assembly wherein the outer sleeve may be compressed upon installation. A further object of the invention is to provide dynamic medical implant longitudinal connecting members that may be utilized with a variety of bone screws, hooks and other bone anchors. Another object of the invention is to provide a more rigid or solid connecting member portion or segment, if desired, such as a solid rod portion integrally linked to one or more flexible portions or segments. Additionally, it is an object of the invention to provide a lightweight, reduced volume, low profile assembly including at least two bone anchors and a longitudinal connecting member therebetween. Furthermore, it is an object of the invention to provide apparatus and methods that are easy to use and especially adapted for the intended use thereof and wherein the apparatus are comparatively inexpensive to make and suitable for use.

Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.

The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged perspective view of a dynamic fixation longitudinal connecting member according to the invention including first and second rigid rod portions, an inner core, an outer spacer and a pair of support rings, and shown attached to a pair of polyaxial bone screws.

FIG. 2 is an enlarged exploded perspective view of the rigid rod portions of the connecting member of FIG. 1.

FIG. 3 is an enlarged exploded front elevational view of the connecting member of FIG. 1.

FIG. 4 is an enlarged perspective view of the spacer of FIG. 1.

FIG. 5 is an enlarged side elevational view of the spacer of FIG. 1.

FIG. 6 is an enlarged perspective view of the spacer of FIG. 1 with portions removed to show the detail thereof.

FIG. 7 is an enlarged perspective view of one of the support rings of FIG. 1.

FIG. 8 is an enlarged and partial front elevational view of the connecting member of FIG. 1 with portions broken away to show the detail thereof.

FIG. 9 is an enlarged perspective view of a second embodiment of a dynamic fixation longitudinal connecting member according to the invention shown with three bone screws.

FIG. 10 is an enlarged perspective view of a rigid rod portion of the connecting member of FIG. 9.

FIG. 11 is an enlarged perspective view of three rigid rod portions and connecting inner core ties of the connecting member of FIG. 9.

FIG. 12 is an enlarged front elevational view of a third embodiment of a dynamic fixation longitudinal connecting member according to the invention including first and second rigid rod portions, an inner core, an outer spacer, an elastic bumper and a crimping ring, and shown attached to a pair of polyaxial bone screws.

FIG. 13 is an enlarged perspective view of the first rigid rod portion of FIG. 12.

FIG. 14 is an enlarged perspective view of the second rigid rod portion of FIG. 12.

FIG. 15 is an enlarged exploded perspective view of the connecting member of FIG. 12, the spacer having a portion broken away to show the detail thereof.

FIG. 16 is an enlarged exploded front elevational view of the connecting member of FIG. 12, the spacer having a portion broken away to show the detail thereof.

FIG. 17 is an enlarged front elevational view of the connecting member of FIG. 12 with portions broken away to show the detail thereof.

FIG. 18 is an enlarged side elevational view of the spacer shown in FIG. 12.

FIG. 19 is an opposed side elevational view of the spacer of FIG. 18.

FIG. 20 is an enlarged perspective view of a fourth embodiment of a dynamic fixation longitudinal connecting member according to the invention shown with three bone screws.

FIG. 21 is an enlarged exploded perspective view of rigid rod portions, a bumper and a crimping ring of the connecting member of FIG. 20.

FIG. 22 is an enlarged perspective view of one of the spacers of the connecting member of FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. It is also noted that any reference to the words top, bottom, up and down, and the like, in this application refers to the alignment shown in the various drawings, as well as the normal connotations applied to such devices, and is not intended to restrict positioning of the connecting member assemblies of the application and cooperating bone anchors in actual use.

With reference to FIGS. 1-8, the reference numeral 1 generally designates a non-fusion dynamic stabilization longitudinal connecting member assembly according to the present invention. The connecting member assembly 1 is elongate and substantially cylindrical, having a central axis A. The connecting member assembly 1 generally includes first and second substantially rigid members 6 and 7 with a central, dynamic connection or transition portion or segment, generally 8, disposed therebetween. A tie or a plurality of ties 10 link the rigid members 6 and 7 at the central segment 8. The ties 10 may be any flexible elongate material that fastens, secures or unites the rigid members 6 and 7, including, but not limited to cords, threads, strings, bands, or fibers that may be single or multiple strands, including twisted, braided or plaited materials. The illustrated central segment 8 further includes an outer sleeve or spacer 14 and a pair of support rings 16.

Each of the illustrated rigid members 6 and 7 are substantially cylindrical with one or more circular cross-sections along a length thereof. However, it is foreseen that the members 6 and 7 may have other forms, including but not limited to oval, square and rectangular cross-sections as well as other curved or polygonal shapes. It is foreseen that the member 6 and 7 may be of different materials, different shapes or different sizes, and thus one member may be more rigid or more flexible than the other member. The members 6 and 7 each are of a length for cooperating with at least one and up to a plurality of bone attachment members, such as bone screws or hooks. The member 6 is substantially solid, rigid and cylindrical and further includes a buttress or plate 20 having a plurality of apertures in the form of through bores 22. The member 7 is also substantially solid, rigid and cylindrical and includes a buttress or plate 24 similar or identical to the plate 20. The plate 24 also has a plurality of apertures in the form of through bores 26 running therethrough that are identical or similar to the apertures 22. Each of the bores 22 and 26 extends through the respective plate 20 and 24 at an oblique angle with respect to the axis A. It is foreseen that according to the invention the bores 22 and 26 may also run parallel to the axis A. It is foreseen that the cord, cords, strands or fibers could be embedded into or adhered on the ends of the members 6 and 7.

With particular reference to FIG. 2, in the illustrated embodiment, there is shown six bores 22 a, 22 b, 22 c, 22 d, 22 e and 22 f and six cooperating bores 26 a, 26 b, 26 c, 26 d, 26 e and 26 f, each oriented substantially uniformly about the axis A. With reference to both FIGS. 2 and 3, in the illustrated embodiment, the ties 10 are in the form of six independent closed loops, 10 a, 10 b, 10 c, 10 d, 10 e and 10 f, oriented in a crisscross pattern, that attach or tether the rigid members 6 and 7 together at the respective plates 20 and 24. The loops are installed individually, with the individual cords 10 being at least one of knotted, adhered, bonded or melted, to form such a closed loop after threading though two adjacent bores in each of the plates 20 and 24. For example, one looped cord 10 extends through the bores 22 a and 22 b, looping about the plate 20 at a location between the bores 22 a and 22 b, and also extends through the bores 26 d and 26 e, looping about the plate 24 at a location between the bores 26 d and 26 e. While, in similar fashion, another cord 10 loops about the plate 22 by extending through the bores 22 d and 22 e and also about the plate 24 by extending through the bores 26 a and 26 b. As illustrated in FIG. 3, orienting the individual loops 10 a-10 f in such a crisscross pattern provides a resulting dynamic corded section 8 that slopes or angles inwardly toward the axis A at or near a central location 28 thereof, providing adequate clearance and ready acceptance of the spacer 14 as will be described in greater detail below. It is foreseen that the cords 10 may be individually looped in a configuration substantially parallel to the axis A or a variety of other orientations.

The ties 10 making up the individual or closed loops may be made from a variety of materials, including polyester or other plastic fibers, strands or threads, such as polyethylene-terephthalate. Such cord and cord-like materials usually are placed under axial tension prior to final installation, for example, the loops 10 a-10 f that are attached to the plates 20 and 24 may be tensioned along the axis A for a selected time prior to installation of the spacer 14 to allow the cords 10 to lengthen and otherwise deform during a primary creep stage. As will be described in more detail below, after the cords 10 reach secondary or steady-state creep, further tension is then placed on the cords 10 in preparation for installation of the spacer 14 between the plates 20 and 24 to ensure dynamic pre-loading of the connector 1, with the corded loops 10 a-10 f being in tension along the axis A while at the same time the spacer 14 is in compression along the axis A. It is also foreseen that in alternative embodiments of the invention, greater or fewer than six discrete loops or even a single tie 10 may be laced through numerous apertures in the plates 20 and 24 to connect the member 6 to the member 7.

Cords 10 of the invention typically do not illustrate elastic properties, such as any significant additional axial distraction after the assembly 1 is operatively assembled. However, it is foreseen that in some embodiments, the ties or cords 10 may be made of a plastic or rubber (natural or synthetic) having elastic properties, allowing for some further distraction of the central connection portion 8 at the ties 10 during operation thereof.

Returning to the longitudinal connecting member rigid members 6 and 7, each of the plates 20 and 24 include respective outer planar surfaces or faces 30 and 34 that operatively face toward one another. Furthermore, each plate 20 and 24 has a respective opposed face 36 and 38. The bores 22 a-f open at both the faces 30 and 36 and the bores 26 a-f open at both the faces 34 and 38. As illustrated in FIGS. 3 and 8, the cords 10 that form the six discrete closed loops, contact the faces 36 and 38 and attach the plate 20 to the plate 24 with the substantially planar surfaces 30 and 34 facing each other. Extending from the faces 36 and 38 are respective elongate cylindrical portions 40 and 42 of the rigid members 6 and 7. The portion 40 terminates at an end 44 and the portion 42 terminates at an end 46. The portions 40 and 42 are each sized and shaped to attach to at least one bone anchor as will be described in greater detail below. The illustrated portions 40 and 42 are approximately the same size, but it is foreseen that different sizes, lengths and shapes are possible, as well as making the portions 40 and 42 from different materials and also making the plates 20 and 24 from materials that are different than the portions 40 and 42. In the illustrated embodiment, the plates 20 and 24 are integral with respective elongate portions 40 and 42 with the members 6 and 7 being made from metal, metal alloys or other suitable materials, including plastic polymers such as polyetheretherketone (PEEK), ultra-high-molecular weight-polyethylene (UHMWP), polyurethanes and composites, including composites containing carbon fiber.

With particular reference to FIGS. 3-6 and 8, the sleeve or spacer 14 advantageously cooperates with the cords 10 of the central connection or transition portion 8, providing limitation and protection of movement of the cords 10. The spacer 14 also protects patient body tissue from damage that might otherwise occur in the vicinity of the corded central portion 8. The spacer 14 is substantially cylindrical and made from a plastic, such as a thermoplastic elastomer made from a polyurethane or polyurethane blend. The spacer 14 has an external substantially cylindrical outer surface 50 and an internal surface 52 defining a through bore. The internal surface 52 is further defined by a centrally located surface 53 having a circular cross section and a pair of outwardly extending substantially conical surfaces 56 and 57 running from the surface 53 to respective substantially planar end surfaces 60 and 62. When cooperating with the looped cords 10, the end surfaces 60 and 62 are substantially perpendicular to the axis A and the crisscross orientation of the looped cords 10 follow the conical inner surfaces 56 and 57 of the spacer 14 with the central portion 28 of the looped cords being substantially aligned with the inner surface 53. It is foreseen that in some embodiments, the spacer may be of circular, square, rectangular or other cross-section including curved or polygonal shapes. In the illustrated embodiment, the spacer 14 further includes a compression groove 64 and a pair of grooves 66 on either side of the groove 64 sized and shaped to receive the support rings or bands 16. Spacers according to the invention may include one, none or any desired number of grooves. The illustrated grooves 64 and 66 are substantially uniform and circular in cross-section, being formed in the external surface 50 and extending radially toward the internal surface 52. The size of the internal surface 52 allows for some axially directed sliding movement of the spacer 14 with respect to the cords 10 of the section 8. The spacer 14 further includes a radially directed elongate slit or gap opening 68 extending therethrough between the outer surface 50 and the inner surface 52 and through the end surfaces 60 and 62. With reference to FIG. 3, the slit or gap 68 allows for opening the spacer 14 and placing the spacer 14 onto the cords 10 of the section 8 with the gap or slit 68 widening or expanding to receive the cords 10 and then elastically returning the spacer 14 to an original cylindrical shape as shown in FIG. 8, but now positioned with the inner cylindrical surface 52 in sliding, rotating engagement with the cords 10 of the section 8. Also, as shown in FIG. 8, when the spacer 14 is initially placed on the cords 10, the spacer 14 completely surrounds the cords 10 and abuts against the buttress plate surfaces 30 and 34. The cords 10 and cooperating compressible spacer 14 allows for some twist or turn, providing some relief for torsional stresses. The spacer 14, however limits such torsional movement as well as bending movement, providing spinal support, as well as allowing for further compression of the assembly 1 at the transition segment 8. It is noted that in addition to limiting the bendability of the central connection portion 8 and thus providing strength and stability to the assembly 1, the spacer 14 also keeps scar tissue from growing into the portion 8 through the cords 10, thus eliminating the need for a sheath-like structure to be placed, adhered or otherwise applied to the cords 10 on the central connection portion 8. In order to reduce the production of any micro wear debris, that in turn may cause inflammation, the spacer 14 inner surfaces and/or cooperating cord 10 surfaces may be coated with an ultra thin, ultra hard, ultra slick and ultra smooth coating, such as may be obtained from ion bonding techniques and/or other gas or chemical treatments.

With reference to FIGS. 3 and 7, the support rings or bands 16 are annular and sized and shaped to encircle the spacer 14 and be closely received in the grooves 66. Support rings 16 may be made from a variety of materials, including metals, metal alloys and plastics. A preferred material is tantalum. In the illustrated embodiment, the rings 16 are of circular cross-section and each include a slit or gap 70. The slit or gap 70 allows for opening the ring 16 and placing the ring 16 about the spacer 14 and into one of the grooves 66 with the gap or slit 70 widening or expanding to receive the spacer 14 and then elastically returning the ring 16 to an original circular orientation as shown in FIG. 8, but now positioned about the spacer 14 and within one of the grooves 66. A spot weld, adhesive, or other attachment is then applied to close the slit 70 and secure the ring 16 to itself and about the spacer 14. The pair of rings 16 thus uniformly surround the spacer 14 about the axis A and near each end surface 60 and 62, preventing a gap or gaps from forming at the slit 68. It is foreseen that according to the invention, the support rings or bands may be made of a tough elastic material and therefore not require the slit 70. During installation, the member 6 or 7 would be received by such a band and then the band would be stretched about the spacer 14 and allowed to return to its original form in one of the grooves 66. In a preferred connector 1 of the invention wherein the members 6 and 7 are made from PEEK and cooperate with polyethylene cords 10 and a polyurethane spacer 14, an assembly 1 that is radiolucent results. In such an embodiment, it may be desirable to make the support rings 16 from a metal or metal alloy, such as tantalum, to provide x-ray orientation markers.

The dynamic connecting member assembly 1 cooperates with at least a pair of bone anchors, such as polyaxial bone screws, generally 75, and cooperating closure structures 77 shown in FIG. 1, the assembly 1 being captured and fixed in place at the rigid end portions 40 and 42 by cooperation between the bone screws 75 and the closure structures 77. The dynamic section 8, that is pre-loaded and pre-tensioned, is disposed between the bone screws 75.

It is noted that an advantageous connecting member 1 according to the invention includes a portion 42 made from a metal alloy such as stainless steel that is elongate and intended for fusion along a major portion or section of the spine, for example, the portion 42 may be sized to extend from the sacrum to the thoracic spinal segment T10. Such an elongate portion 42 is thus connectable to a plurality of bone anchors along the spine. Such a connecting member further includes a dynamic section 8, having cords 10 and spacer 14 that is sized for placement, for example, between T9 and T8. Such an embodiment is believed to minimize rapid degeneration and compressive fractures that tend to occur near ends of such elongate connecting member assemblies.

Because the portions 40 and 42 are substantially solid and cylindrical, the connecting member assembly 1 may be used with a wide variety of bone anchors already available for cooperation with rigid rods including fixed, monoaxial bone screws, hinged bone screws, polyaxial bone screws, and bone hooks and the like, with or without compression inserts, that may in turn cooperate with a variety of closure structures having threads, flanges, or other structure for fixing the closure structure to the bone anchor, and may include other features, for example, break-off tops and inner set screws. The bone anchors, closure structures and the connecting member assembly 1 are then operably incorporated in an overall spinal implant system for correcting degenerative conditions, deformities, injuries, or defects to the spinal column of a patient.

The illustrated polyaxial bone screws 75 each include a shank 80 for insertion into a vertebra (not shown), the shank 80 being pivotally attached to an open receiver or head 81. The shank 80 includes a threaded outer surface and may further include a central cannula or through-bore disposed along an axis of rotation of the shank to provide a passage through the shank interior for a length of wire or pin inserted into the vertebra prior to the insertion of the shank 80, the wire or pin providing a guide for insertion of the shank 80 into the vertebra. The receiver 81 has a pair of spaced and generally parallel arms 85 that form an open generally U-shaped channel therebetween that is open at distal ends of the arms 85. The arms 85 each include radially inward or interior surfaces that have a discontinuous guide and advancement structure mateable with cooperating structure on the closure structure 77. The guide and advancement structure may take a variety of forms including a partial helically wound flangeform, a buttress thread, a square thread, a reverse angle thread or other thread like or non-thread like helically wound advancement structure for operably guiding under rotation and advancing the closure structure 77 downward between the receiver arms 85 and having such a nature as to resist splaying of the arms 85 when the closure 77 is advanced into the U-shaped channel. For example, a flange form on the illustrated closure 77 and cooperating structure on the arms 85 is disclosed in Applicant's U.S. Pat. No. 6,726,689, which is incorporated herein by reference.

The shank 80 and the receiver 81 may be attached in a variety of ways. For example, a spline capture connection as described in Applicant's U.S. Pat. No. 6,716,214, and incorporated by reference herein, may be used for the embodiment disclosed herein. Polyaxial bone screws with other types of capture connections may also be used according to the invention, including but not limited to, threaded connections, frictional connections utilizing frusto-conical or polyhedral capture structures, integral top or downloadable shanks, and the like. Also, as indicated above, polyaxial and other bone screws for use with connecting members of the invention may have bone screw shanks that attach directly to the connecting member portion or segment 40 or 42, or may include compression members or inserts that cooperate with the bone screw shank, receiver and closure structure to secure the connecting member assembly 1 to the bone screw and/or fix the bone screw shank at a desired angle with respect to the bone screw receiver that holds the longitudinal connecting member assembly 1. It is foreseen that if the connecting member portions 40 and 42 are fabricated from a plastic such as polyetheretherketone (PEEK), it may be desirable to utilize bone screws that include one or both upper and lower compression inserts that have a saddle or U-shape configuration to closely engage such segments within the bone screw receiver. Although the closure structure 77 of the present invention is illustrated with the polyaxial bone screw 75 having an open receiver or head 81, it is also foreseen that a variety of closure structures may be used in conjunction with any type of medical implant having an open or closed head, including monoaxial bone screws, hinged bone screws, hooks and the like used in spinal surgery.

To provide a biologically active interface with the bone, the threaded shank 80 may be coated, perforated, made porous or otherwise treated. The treatment may include, but is not limited to a plasma spray coating or other type of coating of a metal or, for example, a calcium phosphate; or a roughening, perforation or indentation in the shank surface, such as by sputtering, sand blasting or acid etching, that allows for bony ingrowth or ongrowth. Certain metal coatings act as a scaffold for bone ingrowth. Bio-ceramic calcium phosphate coatings include, but are not limited to: alpha-tri-calcium phosphate and beta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate (Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, is desirable as hydroxyapatite is chemically similar to bone with respect to mineral content and has been identified as being bioactive and thus not only supportive of bone ingrowth, but actively taking part in bone bonding.

With reference to FIG. 1, the closure structure 77 can be any of a variety of different types of closure structures for use in conjunction with the present invention with suitable mating structure on the interior surface of the upstanding arms 85 of the receiver 81. The illustrated closure structure 77 is rotatable between the spaced arms 85, but could be a slide-in closure structure. As described above, the illustrated closure structure 77 is substantially cylindrical and includes an outer helically wound guide and advancement structure in the form of a flange form 88 that operably joins with the guide and advancement structure disposed on the interior of the arms 85. The illustrated closure structure 77 includes a lower or bottom surface that is substantially planar and may include a point and/or a rim protruding therefrom for engaging the portion 40 or 42 outer cylindrical surface. The closure structure 77 has a top surface 90 with an internal drive feature 92, that may be, for example, a star-shaped drive aperture sold under the trademark TORX. A driving tool (not shown) sized and shaped for engagement with the internal drive feature 92 is used for both rotatable engagement and, if needed, disengagement of the closure 77 from the arms 85. The tool engagement structure 92 may take a variety of forms and may include, but is not limited to, a hex shape or other features or apertures, such as slotted, tri-wing, spanner, two or more apertures of various shapes, and the like. It is also foreseen that the closure structure 77 may alternatively include a break-off head designed to allow such a head to break from a base of the closure at a preselected torque, for example, 70 to 140 inch pounds. Such a closure structure would also include a base having an internal drive to be used for closure removal.

In use, at least two bone screws 75 are implanted into vertebrae for use with the longitudinal connecting member assembly 1. Each vertebra may be pre-drilled to minimize stressing the bone. Furthermore, when a cannulated bone screw shank is utilized, each vertebra will have a guide wire or pin (not shown) inserted therein that is shaped for the bone screw cannula of the bone screw shank 80 and provides a guide for the placement and angle of the shank 80 with respect to the cooperating vertebra. A further tap hole may be made and the shank 80 is then driven into the vertebra by rotation of a driving tool (not shown) that engages a driving feature on or near a top portion of the shank 80. It is foreseen that the screws 75 and the longitudinal connecting member assembly 1 can be inserted in a percutaneous or minimally invasive surgical manner.

With particular reference to FIGS. 2, 3 and 8, the longitudinal connecting member assembly 1 is factory assembled to include the looped ties 10 that are initially tensioned to steady state and thereafter further tensioned to receive the spacer 14 that is cut to a desired size so that the spacer 14 is axially compressed between the plates 20 and 24 after insertion of the spacer 14 about the cords or ties 10 and between such plates 20 and 24. In such process, the spacer 14 is opened or expanded at the slit 68 and moved into position over the cords 10 of the central portion 8 and between the plates 20 and 24 and then allowed to elastically return to an original cylindrical form as shown in FIG. 8. The spacer 14 is also axially compressed during insertion such that the spacer 14 easily slides and is received between the surfaces 30 and 34. Thereafter, the rings or bands 16 are expanded at the respective slits 70 and moved into position in the grooves 66, followed by spot welding thereof to result in closed rings 16 encircling the spacer 14. The resulting connecting member assembly 1 is thus dynamically loaded with the cords 10 in tension and the spacer 14 in compression. In some embodiments according to the invention it may be desirable to place one or more pins through the plates 20 and 24 and into the spacer 14 to prevent rotation of the spacer 14 about the axis A relative to the plates 20 and 24. It may also be desirable to use such pins as x-ray markers.

With further reference to FIG. 1, the pre-loaded connecting member assembly 1 is eventually positioned in an open or percutaneous manner in cooperation with the at least two bone screws 75 with the cords 10 and the spacer 14 disposed between and spaced from the two bone screws 75 and with the portions 40 and 42 each being within a U-shaped channel of a cooperating bone screw 75. It is noted that the portions 40 and/or 42 near respective ends 44 and 46 may be selectively trimmed or cut to size before or at the time of surgery, or if longer, attached to the spine with additional bone anchors. Once a desired position is attained, a closure structure 77 is then inserted into and advanced between the arms 85 of each of the bone screws 75. The closure structure 77 is rotated, using a tool (not shown) engaged with the inner drive 92 until a selected pressure is reached at which point the section 40 or 42 is urged toward, but not completely seated in the U-shaped channel of the bone screw 75. For example, about 80 to about 120 inch pounds pressure may be required for fixing the bone screw shank 80 with respect to the receiver 81 at a desired angle of articulation.

The assembly 1 is thus substantially dynamically loaded and oriented relative to the cooperating vertebra, providing relief (e.g., shock absorption) and protected movement with respect to flexion, extension, distraction and compressive forces placed on the assembly 1 and the two connected bone screws 75. The looped cords 10 and the spacer 14 allow for some twisting or turning, providing some relief for torsional stresses. Furthermore, the compressed spacer 14 places some limits on torsional movement as well as bending movement, to provide spinal support. The pre-loaded cords 10 (in tension) and spacer 14 (in compression) allow for compression and some extension of the assembly 1 located between the two bone screws 75, e.g., shock absorption.

If removal of the assembly 1 from any of the bone screw assemblies 75 is necessary, or if it is desired to release the assembly 1 at a particular location, disassembly is accomplished by using the driving tool (not shown) with a driving formation cooperating with the closure structure 77 internal drive 92 to rotate and remove the closure structure 77 from the receiver 81. Disassembly is then accomplished in reverse order to the procedure described previously herein for assembly.

Eventually, if the spine requires more rigid support, the connecting member assembly 1 according to the invention may be removed and replaced with another longitudinal connecting member, such as a solid rod, having the same diameter as the portions 40 and 42, utilizing the same receivers 81 and the same or similar closure structures 77. Alternatively, if less support is eventually required, a less rigid, more flexible assembly, for example, an assembly 1 having portions 40 and 42 made of a more flexible material, but with the same diameter as the rigid portions 40 and 42, may replace the assembly 1, also utilizing the same bone screws 75.

With reference to FIGS. 9-11, an alternative longitudinal connecting member assembly according to the invention, generally 101, has a central axis B and includes rigid members 105, 106 and 107 and first and second dynamic connection portions or sections 108 and 108A. The dynamic sections 108 and 108A include respective closed looped cords 110 and 110A, respective spacers 114 and 114A and respective support rings 116 and 116A. The connecting member assembly 101 provides for two dynamic support sections between a plurality of vertebrae. The illustrated embodiment is shown attached to three bone screws 75 and cooperating closure structures 77 previously described herein. The illustrated rigid members 105, 106 and 107 are each sized for attachment to a single bone anchor or screw. However, it is noted that each such rigid member 105, 106 and 107 may be of greater length (along the axis B) for operative attachment to two or more bone anchors. Furthermore, more than one rigid member 105 may be disposed between rigid members 106 and 107 to provide a plurality of dynamic sections.

The illustrated members 106 and 107 are identical or substantially similar to respective members 6 and 7 previously described herein with respect to the connecting member 1, the member 106 having an end plate 120 and a plurality of bores 122 similar to the plate 20 and bores 22 previously described herein and the member 107 having an end plate 124 and a plurality of bores 126 similar to the plate 24 and bores 26 previously described herein with respect to the member 7. Also, the closed looped cords 110 and 110A are identical or substantially similar to the closed looped cords 10 previously described herein with respect to the connecting member 1 with the cooperating spacers 114 and 114A being identical or substantially similar to the spacer 14 previously described herein with respect to the connecting member 1. Also, the support rings 116 and 116A are identical or substantially similar to the support rings 16 previously described herein with respect to the connecting member 1. However, in the connecting member 101, rather than having closed looped cords that directly attach the members 106 and 107 as previously described with respect to the members 6 and 7, the closed looped cords 110 attach the member 105 with the member 106 and the closed looped cords 110A attach the member 105 with the member 107 in a manner substantially identical to what has been described herein with respect to the close looped cords 10 of the connecting member 1.

Thus, the member 105 may also be considered to be an extender member that is disposed between the members 106 and 107 and is attached to each of such members with the respective closed looped cords 110 and 110A to provide an additional dynamic segment to the assembly 101. The illustrated member 105 includes a pair of opposed end plates 182 and 183 and an integral cylindrical mid-portion 184 extending therebetween. The end plates 182 and 183 are identical or substantially similar to the plates 20 and 24 previously described herein with respect to the members 6 and 7. Thus, the end plates 182 and 183 include respective apertures or through bores 186 and 187 for receiving the respective closed looped cords 110 and 110A. In the illustrated embodiment there are six bores 186 cooperating with the six bores 122 of the member 6 and six bores 187 for cooperating with the six bores 126 of the member 107. The looped cords 110 loop through the bores 122 and the bores 186 while the looped cords 110A loop through the bores 126 and the bores 187. The illustrated cylindrical mid-portion 184 is sized to be received between arms 85 of at least one bone screw 75.

In use, the closed looped cords 110 and 110A are installed in the same manner as previously described herein with respect to the closed looped cords 10 and the spacers 114 and 114A and cooperating support rings 116 and 116A are installed in the same manner as previously described herein with respect to the spacer 14 and the rings 16. Thereafter, the pre-tensioned, pre-compressed connecting member 101 is positioned in an open or percutaneous manner in cooperation with the at least three bone screws 75 with the cords 110 and 110A and cooperating spacers 114 and 114A each disposed between and spaced from such bone screws 75 and portions of the members 105, 106 and 107 each being within a U-shaped channel of a cooperating bone screw 75. A closure structure 77 is then inserted into and advanced between the arms 85 of each of the bone screws 75 to capture and lock the connecting member 101 in a desired location and position along the spine. Disassembly, removal and replacement of the connecting member assembly 101 with a more or less rigid connecting member may be performed in a manner as previously described herein with respect to the connecting member assembly 1.

With reference to FIGS. 12-19, another alternative longitudinal connecting member assembly according to the invention, generally 201 is elongate and substantially cylindrical, having a central axis C. The connecting member assembly 201 generally includes a first rigid anchor member 206 and a second rigid terminal member 207. A central, dynamic connection or transition portion or segment, generally 208, is disposed between the members 206 and 207. A tie, cord or a plurality of ties or cords 210 loop about and through apertures of the anchor member 206 and extend through a bore in the terminal member 207. The ties 210 may be any flexible elongate material that fastens, secures or unites the rigid members 206 and 207, including, but not limited to cords, threads, strings, bands, or fibers that may be single or multiple strands, including twisted, braided or plaited materials. The illustrated central segment 208 further includes a closed, non-slitted outer sleeve or spacer 214. The assembly 201 further includes an elastic bumper 217 and a crimping ring 219.

Each of the illustrated rigid members 206 and 207 are substantially cylindrical with one or more circular cross-sections along a length thereof. However, it is foreseen that the members 206 and 207 may have other forms, including but not limited to oval, square and rectangular cross-sections as well as other curved or polygonal shapes. It is foreseen that the members 206 and 207 may be of different materials, different shapes or different sizes, and thus one member may be more rigid or more flexible than the other member. The members 206 and 207 each are of a length for cooperating with at least one and up to a plurality of bone attachment members, such as bone screws or hooks.

With particular reference to FIGS. 12, 13 and 17, the anchor member 206 is substantially solid, rigid and cylindrical and further includes a buttress or plate 220 having a plurality of apertures in the form of through bores 222. The member 206 is identical or substantially similar to the member 6 previously described herein with respect to the connecting member assembly 1. The illustrated anchor member 206 has six bores 222 that extend through the plate 220 at an oblique angle with respect to the axis C as best shown in FIG. 17. It is foreseen that according to the invention the bores 222 may also run parallel to the axis C. The ties or cords 210 are in the form of six independent open loops installed individually by looping through pairs of adjacent bores 222 and then extending outwardly away from the plate 220 as shown in FIGS. 15 and 16. Similar to the cords 10 discussed previously herein, the cords 210 are placed under axial tension along the axis C for a selected time prior to final, fixed installation with the other components 214, 207, 217 and 219 to lengthen and otherwise deform the cords 210 during a primary creep stage. After the cords 210 reach secondary or steady-state creep, further tension is then placed on the cords 210 in preparation for final tightening and crimping of the ring 219 as will be described in greater detail below. It is also foreseen that in alternative embodiments of the invention, greater or fewer than six discrete open loops may be laced through apertures in the plate 220 and pulled through the member 207.

The cords 210 of the invention typically do not illustrate elastic properties, such as any significant additional axial distraction after the assembly 201 is operatively assembled. However, it is foreseen that in some embodiments, the ties or cords 210 may be made of a plastic or rubber (natural or synthetic) having elastic properties, allowing for some further distraction of the central connection portion 208 at the ties 210 during operation thereof.

With particular reference to FIG. 14, the terminal member 207 includes a buttress or plate 224 and in inner surface 226 that forms a through bore extending through the entire member 207 in an axial direction, sized and shaped for receiving a length of the bundled cords 210. When operatively connected to the member 206, the bore formed by the inner surface 226 extends along the axis C. With further reference to FIGS. 15-17, each of the plates 220 and 224 include respective outer planar surfaces or faces 230 and 234 that operatively face toward one another. Furthermore, each plate 220 and 224 has a respective opposed face 236 and 238. The bores 222 open at both the faces 230 and 236. The inner surface 226 forming the bore of the member 207 opens at the outer planar surface 234 and also at an end 239. The cords 210 that form the discrete open loops, loop about and contact the face 236, extend along the axis C within the inner surface 226 and extend through the end 239. Extending from and integral to the faces 236 and 238 are respective elongate cylindrical portions 240 and 242 of the respective anchor member 206 and the terminal member 207. The portion 240 terminates at an end 244. The open cords 210 extend completely through the elongate cylindrical portion 242 and into the bumper 217 and the crimping ring 219.

The portions 240 and 242 are each sized and shaped to attach to at least one bone anchor as will be described in greater detail below. The illustrated portions 240 and 242 are approximately the same size and length, but it is foreseen that different sizes, lengths and shapes are possible, as well as making the portions 240 and 242 from different materials and also making the plates 220 and 224 from materials that are different than the portions 240 and 242. In the illustrated embodiment, the plates 220 and 224 are integral with respective elongate portions 240 and 242 with the members 206 and 207 being made from metal, metal alloys or other suitable materials, including plastic polymers such as polyetheretherketone (PEEK), ultra-high-molecular weight-polyethylene (UHMWP), polyurethanes and composites, including composites containing carbon fiber.

With particular reference to FIGS. 15-19, the sleeve or spacer 214 advantageously cooperates with the cords 210 of the central connection or transition portion 208, providing limitation and protection of movement of the cords 210. The spacer 214 also protects patient body tissue from damage that might otherwise occur in the vicinity of the corded central portion 208. The spacer 214 is substantially cylindrical and made from a plastic, such as a thermoplastic elastomer made from a polyurethane or polyurethane blend. The spacer 214 has an external substantially cylindrical outer surface 250 and an internal surface 252 defining a through bore. The internal surface 252 is further defined by a substantially cylindrical surface 253 having a circular cross section and an outwardly extending substantially conical surface 256 running from the surface 253 to a substantially planar end surface 260. The spacer 214 further includes an opposed planar end surface 262. The inner cylindrical surface 253 opens to the end surface 262.

When operatively cooperating with the looped cords 210, the end surfaces 260 and 262 of the spacer 214 are substantially perpendicular to the axis C. Also, when installed within the inner cylindrical surface 226, the cords 210 are drawn inwardly from the bores 222 and toward the axis C. The conical inner surface 256 of the spacer 214 provides clearance for the cords 210 at the plate surface 230 while the cylindrical inner surface 253 aligns the cords 210 with the inner bore formed by the inner surface 226 of the terminal member 207. It is also foreseen that the cords 210 may be twisted or otherwise connected to form a substantially cylindrical unit prior to insertion in the spacer 214 and the terminal member 207. It is foreseen that in some embodiments, the spacer 214 may be of circular, square, rectangular or other cross-section including curved or polygonal shapes. In the illustrated embodiment, the spacer 214 further includes a compression groove 264. Spacers according to the invention may include one, none or any desired number of grooves. The illustrated groove 264 is substantially uniform and circular in cross-section, being formed in the external surface 250 and extending radially toward the internal surface 252. The size of the internal surface 252 allows for some axially directed sliding movement of the spacer 214 with respect to the cords 210. The cords 210 and cooperating compressible spacer 214 allow for some twist or turn, providing some relief for torsional stresses. The spacer 214, however limits such torsional movement as well as bending movement, providing spinal support, as well as allowing for further compression of the assembly 1 at the flexible central connection portion 208. It is noted that in addition to limiting the bendability of the central connection portion 208 and thus providing strength and stability to the assembly 201, the spacer 214 also keeps scar tissue from growing into the portion 208 through the cords 210, thus eliminating the need for a sheath-like structure to be placed, adhered or otherwise applied to the cords 210 on the central connection portion 208. In order to reduce the production of micro wear debris, that in turn may cause inflammation, the spacer 214 inner surfaces and/or cooperating cord 210 surfaces may be coated with an ultra thin, ultra hard, ultra slick and ultra smooth coating, such as may be obtained from ion bonding techniques and/or other gas or chemical treatments.

With particular reference to FIGS. 15 to 17, the bumper 217 is substantially cylindrical, including an outer surface 270 and an inner surface 272 forming a substantially cylindrical through bore that opens at planar end surfaces 274 and 276 and operatively extends along the axis C. The bumper 217 further includes a compression groove 278 that is similar in form and function to the compression groove 264 of the spacer 214. The bumper 217 is sized and shaped to receive the elongate cords 210 through the inner surface 272. The bumper 217 is preferably made from an elastomeric material such as polyurethane. The bumper 217 provides axial elastic distraction of the cords 210 as will be described in greater detail below.

Also with reference to FIGS. 15 to 17, the crimping ring 219 is substantially cylindrical and includes an outer surface 280 and an inner surface 282 forming a substantially cylindrical through bore that opens at planar end surfaces 284 and 286 and operatively extends along the axis C. The crimping ring 219 is sized and shaped to receive the elongate cords 210 through the inner surface 282. The crimping ring 219 further includes a pair of crimp or compression grooves 288 that are pressable and deformable inwardly toward the axis C upon final tensioning of the cords 210 during assembly of the connector 201 to engage and hold the cords 210 in tension and thereby transmit compressive force to the elastic spacer 214. The crimping ring 219 is preferably made from a stiff, but deformable material, including metals and metal alloys. As will be discussed with respect to a further embodiment of the invention described below, the cords 210 may be threaded through two crimping rings 219 placed adjacent to one another, with a preliminary crimping ring being at a terminal end of the assembly 201. Such a preliminary ring is crimped to initially lock the assembly together with the cords 210 in tension. If further creep and deformation of the cords 210 decreases the axial tension on the cords 210 within the assembly 201, the cords 210 may be re-tensioned and locked into place with the second or final crimping ring. The preliminary crimping ring may then be sliced off of the assembly 201 and discarded.

With reference to FIG. 12, the dynamic connecting member assembly 201 cooperates with at least a pair of bone anchors, such as the polyaxial bone screws, generally 75, and cooperating closure structures 77 described previously herein, the assembly 201 being captured and fixed in place at the rigid portions 240 and 242 by cooperation between the bone screws 75 and the closure structures 77. The dynamic section 208, that is pre-loaded and pre-tensioned, is disposed between the bone screws 75.

With particular reference to FIGS. 12 and 15-17, the longitudinal connecting member assembly 201 is factory assembled by looping six ties 210 about and through the bores 222 of the plate 220 of the anchor member 207 to form the twelve strands or cords 210 that are then threaded through the remaining components of the assembly 201. It is noted that the ties 210 may be initially tensioned to steady state and thereafter further tensioned after assembly with the other components. Alternatively, the twelve cords or strands 210 that are anchored to the member 206 are initially passed through the spacer 214 inner surface 252, followed by the terminal member 207 internal surface 226, then the bumper 217 inner surface 272 and finally the crimping ring 219 inner surface 282 and out the end 286. Thereafter, the spacer 214, the terminal member 207, the bumper 217 and the crimping ring 219 are snugged up against the plate 220 of the anchor member 206 and tension is applied to the bundle of twelve cords 210. Tension is increased on the cord bundle 210 until the elastic spacer and the elastic bumper 217 are compressed and the cords have stopped stretching. Thereafter, the crimping ring is crimped using a tool (not shown) that presses on the opposed grooves 288 and deforms toward the axis C to make contact and firmly grip the cords 210, keeping the cords 210 in the desired tension and locking the components of the assembly 201 in place. The resulting connecting member assembly 201 is thus dynamically loaded with the cords 210 in tension and the spacer 214 and elastic bumper 217 in compression. In some embodiments according to the invention it may be desirable to place one or more pins through the plates 220 and 224 and into the spacer 214 to prevent rotation of the spacer 214 about the axis C relative to the plates 220 and 224. It may also be desirable to use such pins as x-ray markers.

With further reference to FIG. 12, the pre-loaded connecting member assembly 201 is eventually positioned in an open or percutaneous manner in cooperation with the at least two bone screws 75 with the spacer 214 disposed between and spaced from the two bone screws 75 and with the portions 240 and 242 each being within a U-shaped channel of a cooperating bone screw 75. A closure structure 77 is then inserted into and advanced between the arms 85 of each of the bone screws 75. The closure structure 77 is rotated, using a tool (not shown) engaged with the inner drive 92 until a selected pressure is reached at which point the section 240 or 242 is urged toward, but not completely seated in the U-shaped channel of the bone screw 75. For example, about 80 to about 120 inch pounds pressure may be required for fixing the bone screw shank 80 with respect to the receiver 81 at a desired angle of articulation.

The assembly 201 is thus substantially dynamically loaded and oriented relative to the cooperating vertebra, providing relief (e.g., shock absorption) and protected movement with respect to flexion, extension, distraction and compressive forces placed on the assembly 201 and the two connected bone screws 75. The looped cords 210 and the spacer 214 allow for some twisting or turning, providing some relief for torsional stresses. Furthermore, the compressed spacer 214 places some limits on torsional movement as well as bending movement, to provide spinal support. The pre-loaded cords 210 (in tension) and spacer 214 (in compression) allow for compression and some extension of the assembly 201 located between the two bone screws 75, e.g., shock absorption. Disassembly, removal and replacement of the connecting member assembly 201 with a more or less rigid connecting member may be performed in a manner as previously described herein with respect to the connecting member assembly 1.

With reference to FIGS. 20-22, another longitudinal connecting member assembly according to the invention, generally 301, has a central axis D and includes an intermediate rigid member 305, a rigid anchor member 306, a rigid terminal member 307 and first and second dynamic connection portions or sections 308 and 308A. An open loop cord bundle 310 extends through both the sections 308 and 308A. The dynamic sections 308 and 308A further include respective spacers 314 and 314A. The connecting member assembly 301 provides for two dynamic support sections between a plurality of vertebrae. The illustrated embodiment is shown attached to three bone screws 75 and cooperating closure structures 77 previously described herein. The illustrated rigid members 305, 306 and 307 are each sized for attachment to a single bone anchor or screw. However, it is noted that each such rigid member 305, 306 and 307 may be of greater length (along the axis D) for operative attachment to two or more bone anchors. Furthermore, more than one rigid member 305 may be disposed between rigid members 306 and 307 to provide a plurality of dynamic sections.

The connecting member assembly 301 is substantially similar to the connecting member assembly 201 previously described herein with the exception of three components: the additional intermediate rigid member 305, the additional spacer 314A and the additional crimping ring 319A. The illustrated members 306 and 307 are identical or substantially similar to respective members 206 and 207 previously described herein with respect to the connecting member 201, the member 306 having an end plate 320 and a plurality of bores 322 similar to the plate 220 and bores 222 previously described herein and the member 307 having an end plate 324 and a through bore 326 similar to the plate 224 and bore 226 previously described herein with respect to the member 207. Also, the open looped cord bundle 310 is identical or substantially similar to the open looped cord bundle 210, with the exception that the bundle 310 is of greater axial length (along the axis D) as compared to the corded bundle 210 previously described herein with respect to the connecting member 201. The spacer 314 that is disposed between the member 306 and the member 305 is identical or substantially similar to the spacer 214 previously described herein with respect to the connecting member 201. Also, the elastic bumper 317 and both crimping rings 319 and 319A are identical or substantially similar to the respective bumper 217 and crimping ring 219 previously described herein with respect to the connecting member 201.

With particular reference to FIGS. 20 and 21, the intermediate rigid member 305 is disposed between the members 306 and 307 and provides for an additional dynamic connection section 308A. In particular, the member 301 includes a pair of opposed end plates 382 and 383 and an integral cylindrical mid-portion 384 that extends therebetween. The end plates 382 and 383 are identical or substantially similar to the plate 324 of the member 307. The member 305 further includes a through bore 386 running through the entire member 305, from the end plate 382 to the end plate 383 and axially centrally through the cylindrical mid-portion 384. The illustrated cylindrical mid-portion 384 is sized to be received between arms 85 of at least one bone screw 75.

The spacer 314 receives the cord bundle 310 at a location between the plate 320 of the anchor member 306 and the plate 382 of the intermediate rigid member 305. The spacer 314A receives the cord bundle 310 at a location between the plate 383 of the member 305 and the plate 324 of the terminal member 307. The illustrated spacer 314A is substantially similar to the spacer 314 and the spacer 214 previously described herein with respect to the connecting member assembly 201, having an outer cylindrical surface 390, an inner surface 392 defining a through bore running between planar surfaces 394 and 395 and at least one outer compression groove 396. However, unlike the spacers 214 and 314, the inner surface 392 of the spacer 314A is cylindrical and defines a bore of constant circular cross-section sized and shaped to receive a length of the cord bundle 310.

In use, the open looped cord bundle 310 is installed on the anchor member 306 by looping through the apertures 322 in the same manner as previously described herein with respect to the installation of the open looped cord bundle 210 through the apertures 222. The twelve cords or strands 310 that are anchored to the member 306 are initially passed through the bore in the spacer 314, followed by the bore formed by the intermediate member 305 internal cylindrical surface 386, then the bore formed by the spacer 314A internal surface 392, followed by the bore formed by the terminal member 307 internal surface 326, then the bore of the bumper 317, the bore of the crimping ring 319 and finally through the bore of the crimping ring 319A. Thereafter, the spacer 314, the intermediate member 305, the spacer 314A, the terminal member 307, the bumper 317, the crimping ring 319 and the crimping ring 319A are snugged up against the plate 320 of the anchor member 306 and tension is applied to the bundle of twelve cords 310. Tension is increased on the cord bundle 310 until the elastic spacers 314 and 314A and the elastic bumper 317 are compressed and the cords 310 have stopped stretching. Thereafter, the end crimping ring 319A is crimped using a tool (not shown) that presses on opposed grooves of the ring 319A and deforms the ring toward the axis D to make contact and firmly grip the cords 310. If viscoelastic changes decrease the axial tension in the cord bundle 310, the assembly 301 may be re-tensioned by pulling the cords 310 away from the anchor member 306 until a desired tension is again reached. At that time, the other crimping ring 319 is crimped using a tool (not shown) that presses on opposed grooves of the ring 319 and deforms the ring toward the axis D to make contact and firmly grip the cords 310. Thereafter, the crimping ring 319A is sliced off of the assembly 301. The resulting connecting member assembly 301 is thus dynamically loaded with the cords 310 in tension with the spacers 314 and 314A and the elastic bumper 317 in compression.

With further reference to FIG. 20, the pre-loaded connecting member assembly 301 is eventually positioned in an open or percutaneous manner in cooperation with the at least three bone screws 75 with the spacers 314 and 314A disposed between and spaced from the bone screws 75 and with cylindrical portions of each of the members 305, 306 and 307 being within a U-shaped channel of a cooperating bone screw 75. A closure structure 77 is then inserted into and advanced between the arms 85 of each of the bone screws 75. The closure structure 77 is rotated, using a tool (not shown) engaged with the inner drive 92 until a selected pressure is reached, for example, about 80 to about 120 inch pounds pressure may be required for fixing the bone screw shank 80 with respect to the receiver 81 at a desired angle of articulation.

The assembly 301 is thus substantially dynamically loaded and oriented relative to the cooperating vertebra, providing relief (e.g., shock absorption) and protected movement with respect to flexion, extension, distraction and compressive forces placed on the assembly 301 and the three connected bone screws 75. The cords 310 and the spacers 314 and 314A allow for some twisting or turning, providing some relief for torsional stresses. Furthermore, the compressed spacers 314 and 314A place some limits on torsional movement as well as bending movement, to provide spinal support. The pre-loaded cords 310 (in tension) and spacers 314 and 314A (in compression) allow for compression and some extension of the assembly 301 located between the two bone screws 75, e.g., shock absorption. Disassembly, removal and replacement of the connecting member assembly 301 with a more or less rigid connecting member may be performed in a manner as previously described herein with respect to the connecting member assembly 1.

It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown. 

1. In a medical implant assembly having at least first and second bone anchors cooperating with a longitudinal connecting member, the improvement wherein the connecting member comprises: a) a first substantially solid connecting member portion for attachment to the first bone anchor, the first connecting member having at least a pair of spaced apertures; b) a second connecting member portion for attachment to the second bone anchor; and c) a transition portion disposed between the first and second connecting member portions, the transition portion having at least one flexible tie looped through the pair of spaced apertures of the first connecting member portion.
 2. The improvement of claim 1 wherein the first connecting member portion is substantially rigid.
 3. The improvement of claim 1 wherein the second connecting member portion is substantially rigid.
 4. The improvement of claim 1 wherein the first connecting member portion has a plurality of apertures and the at least one tie is a plurality of closed loops.
 5. The improvement of claim 1 wherein the second connecting member portion has a through bore and the at least one tie is received through the through bore.
 6. The improvement of claim 1 wherein the transition portion further comprises an elastic outer spacer.
 7. The improvement of claim 6 wherein the at least one tie is in tension and the elastic outer spacer is in compression.
 8. In a medical implant assembly having at least two bone attachment structures cooperating with a longitudinal connecting member, the improvement wherein the connecting member comprises: a transition portion disposed between the bone attachment structures, the transition portion having a) at least one substantially rigid portion with at least a pair of spaced apertures; and b) at least one elongate tie extending through the apertures, the tie being in tension prior to attachment of the rigid portion to the bone attachment structure.
 9. The improvement of claim 8 wherein the at least one substantially rigid portion is a first rigid portion having a plurality of apertures and further comprising a second rigid portion having at least a second aperture, the at least one tie extending through each of the apertures.
 10. The improvement of claim 8 wherein the at least one rigid portion has a plurality of apertures and further comprising a plurality of ties, each tie extending through an aperture.
 11. The improvement of claim 9 wherein both the first and second rigid portions have a plurality of apertures and further comprising a plurality of ties, each tie extending through one aperture of the first rigid portion and one aperture of the second portion, the ties forming discrete loops.
 12. The improvement of claim 9 wherein the first rigid portion is an elongate rod.
 13. The improvement of claim 9 wherein both the first and second rigid portions are each elongate rods.
 14. The improvement of claim 9 further comprising a compressible spacer at the transition portion.
 15. In a medical implant assembly having at least first and second bone anchors cooperating with a longitudinal connecting member, the improvement wherein the connecting member comprises: a) first and second rigid ends, the first rigid end coupled to the first bone anchor, the first rigid end extending completely through the first bone anchor; the second rigid end coupled to the second bone anchor, the second rigid end extending completely through the second bone anchor; b) a pre-tensioned non-metallic flexible core positioned between the first and second rigid ends and coupled to both the first and second rigid ends; and c) a pre-compressed elastomer completely surrounding the flexible core.
 16. The improvement of claim 15 wherein the first rigid end has an integral plate with at least a pair of apertures and the flexible core is at least one tie looped through the apertures.
 17. The improvement of claim 15 wherein both the first rigid end and the second rigid end each have a plurality of apertures and the flexible core is at least one tie extending through each of the apertures.
 18. The improvement of claim 15 wherein the first rigid end has a plurality of apertures and the flexible core comprises a plurality of ties, each tie extending through an aperture.
 19. The improvement of claim 18 wherein the second rigid end has a plurality of apertures and each tie extends through at least one aperture of the first rigid end and one aperture of the second rigid end, the ties forming discrete loops.
 20. The improvement of claim 19 wherein the first rigid end includes an elongate rod integral with a radially extending plate, the plate having the plurality of apertures. 